freeCodeCamp/curriculum/challenges/espanol/07-scientific-computing-with-python/learn-algorithm-design-by-building-a-shortest-path-algorithm/655790d113d14dbb727eaf41.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
655790d113d14dbb727eaf41	Step 45	20	step-45

--description--

Once the distance to a node is set inside the distances dictionary, you need to keep track of the path to that node, too. If the distance for the node in the processed tuple has been updated, the last item in its path is the node itself.

Inside your conditional, nest another if statement that triggers when the last element of paths[node] is equal to node. Use pass to fill the if statement body.

--hints--

You should create a nested if statements that checks if paths[node][-1] is equal to node. Don't forget to use pass.

({ test: () =>  {
    const shortest = __helpers.python.getDef(code, "shortest_path");
    const {function_body} = shortest;    
    assert(function_body.match(/^(\s*)if.*:.*^\1(\s{4})if\s+paths\s*\[\s*node\s*\]\s*\[\s*-\s*1\s*\]\s*==\s*node\s*:\s*^\1\2\2pass/ms));
  }
})

--seed--

--seed-contents--

my_graph = {
    'A': [('B', 3), ('D', 1)],
    'B': [('A', 3), ('C', 4)],
    'C': [('B', 4), ('D', 7)],
    'D': [('A', 1), ('C', 7)]
}

def shortest_path(graph, start):
    unvisited = list(graph)
    distances = {node: 0 if node == start else float('inf') for node in graph}
    paths = {node: [] for node in graph}
    paths[start].append(start)
--fcc-editable-region--    
    while unvisited:
        current = min(unvisited, key=distances.get)
        for node, distance in graph[current]:
            if distance + distances[current] < distances[node]:
                distances[node] = distance + distances[current]
--fcc-editable-region--    
    print(f'Unvisited: {unvisited}\nDistances: {distances}\nPaths: {paths}')

#shortest_path(my_graph, 'A')